1. Field of the Invention
The present invention relates to a light source device provided with a laser light source, and a projector device which is a projection type image display device provided with such a light source device.
2. Description of the Background Art
Recently, as a light source used in a large-sized high brightness projector device for a large hall or a digital cinema, in intermediate-sized or small-sized projector device mainly used for a conference or presentation with a small number of participants, in a projection monitor which incorporates a projection optical system and a large-sized screen in a house or the like, a light source which uses a semiconductor light source such as an LED or a laser diode has been popularly available as commercial products, and various proposals have been made concerning such a semiconductor light source. These devices can acquire the following advantageous effects by using the semiconductor light source in place of a lamp which has been conventionally used as a light source for many projector devices and projection monitors. One advantage is that these devices have a broader color reproduction range. Another advantage is that these devices can be turned on instantaneously. Still another advantage is that these devices consume a small amount of electricity. Still another advantage is that these devices have a long lifetime.
Particularly, a laser light source which uses a laser diode also has an advantage that the acquisition of higher brightness and higher output can be realized by overlapping beams. Accordingly, as one application of a large-sized high brightness projector device used for projection on a large screen, the development of the light source device provided with a large number of laser light source modules has been in progress.
In this light source device, an amount of exhaust heat from laser light source modules is increased in proportion to the increase in the number of the laser light source modules. In a large-sized high brightness projector device with several tens of thousands of lumen class, an amount of exhaust heat from the laser light source module reaches a several thousand W level. Cooling by a conventional air cooling method using a heat sink or a heat pipe unit has a significant drawback that the device becomes large-sized since it is necessary to expand a heat radiation area. Such cooling by the conventional air cooling method also has a serious drawback that a blower generates noise in acquiring a large amount of air supply.
It has been also known that a laser light source exhibits higher efficiency as a temperature of a light emitting part is lowered and hence, the laser light source can acquire higher output and a longer lifetime in such a case. On the other hand, the laser light source has a characteristic that a wavelength of the emitted light and laser output change corresponding to a change in a temperature of the light emitting part and hence, it is necessary to provide appropriate cooling which conforms to the specification of the light emitting part.
As means for solving to perform low-temperature cooling to acquire higher outputting of the laser light source, a cooling method which uses a Peltier element has been proposed. Further, it is desirable to adopt a cooling method which further increases heat radiation efficiency by directly or indirectly using a refrigerating cycle using a vapor compression refrigerating machine.
In such a cooling method, it is possible to maintain a temperature of a cooling part which is an object to be cooled at a room temperature or below. Conventionally, to prevent the generation of dew condensation water in the inside of a device during an operation, attempts have been made to maintain the temperature of the cooling part at a dew point or above. However, the increase in a light emission efficiency brought about by lowering the temperature of a light emitting part of the laser light source leads to the acquisition of long lifetime of the light source, the increase in reliability of the light source, the reduction in the number of modules and the suppression of an amount of exhaust heat and hence, the adoption of the cooling method which lowers the temperature of the cooling part equal to or below a dew point and a counter measure to prevent the generation of dew condensation water have been considered as important tasks to be developed.
For example, a technique described in Japanese Patent Application Laid-Open No. 2009-86269 is the invention relating to temperature adjustment means for laser elements arranged in an array. Japanese Patent Application Laid-Open No. 2009-86269 discloses a technique where a heat receiving plate on which the laser elements are arranged is directly brought into contact with a freezing circuit for cooling the laser elements.
For example, a technique described in Japanese Patent Application Laid-Open No. 2009-86273 is the invention for protecting a laser element array from being affected by dew condensation water. Japanese Patent Application Laid-Open No. 2009-86273 discloses a technique where outside air is shut off by forming a synthetic resin layer on a portion where the laser element array is arranged.
For example, a technique described in Japanese Patent Application Laid-Open No. 2006-253274 is the invention relating to a cooling structure of a semiconductor element such as an LED or a laser diode which uses a Peltier element. Japanese Patent Application Laid-Open No. 2006-253274 discloses the technique where dew condensation water is prevented by forming a sealed space on a side where the LED and the Peltier element are cooled in cooling the semiconductor element at a temperature equal to or below an outside air temperature.
However, the device described in Japanese Patent Application Laid-Open No. 2009-86269 takes no countermeasure against dew condensation water and hence, the device has a problem that a defect attributed to dew condensation water may arise. Further, in the device described in Japanese Patent Application Laid-Open No. 2009-86273, the synthetic resin layer formed at the portion where the laser element array is arranged is also cooled in itself and hence, the device has a problem that dew condensation water is generated on a surface of the synthetic resin layer or a problem that it is necessary to increase a thickness of the synthetic resin layer to increase heat insulation property of the synthetic resin layer so that a manufacturing cost is pushed up.
The device described in Japanese Patent Application Laid-Open No. 2006-253274 has a problem that a complicated structure becomes necessary for forming a sealed space on a cooling side of the Peltier element, and the Peltier elements, the number of which is equal to the number of light source modules, are necessary for cooling a large number of light source modules corresponding to a large output and hence, a cost of parts is increased. Further, there exists a possibility that reliability of the degree of closing is lowered caused by an error in assembling a sealed space or a slow leakage from the sealed space.